The invention relates to a storage container, especially for cryogenic liquids, with an inside and an outside container, whereby an insulation space is located between the inside and the outside container and whereby at least one support is provided for increasing the stability of the inside container and/or outside container.
Industrial gases, such as helium, hydrogen, nitrogen, oxygen or LNG (Liquid Natural Gas), are frequently stored or transported in storage containers in the liquid state. Such storage containers are generally designed with double walls, whereby the liquid gas is stored in the inside container, and the intermediate space between the inside container and the outside container is evacuated so as to form a vacuum for insulation.
Excessive forces act both on the inside container, especially when liquid gas is stored under high pressure, and on the outside container due to the vacuum, which in turn make very large wall thicknesses necessary in the case of a storage container design having flat sides. For this reason, the storage containers were previously designed, in most cases, as cylindrical or spherical shapes.
Hydrogen and LNG are used to an increasing extent as fuels for motor vehicles, boats or aircraft. In this case, storage is preferably carried out in liquid form in the above-described pressurized storage containers with vacuum insulation. The cylindrical design of the container commonly used to date adapts poorly to the vehicle geometry, however. Thus, for example, in the so-called low-cradled buses, an attempt is made to provide a tank arrangement in the upper bus area or on the vehicle roof, whereby the tank is to be amply-sized, but as small as possible.
DE-OS 195 24 681 therefore proposes a storage container for cryogenic media that consists of several individual tubular containers that communicate with one another on the liquid side and that are surrounded by a common outside insulation container that generally does not have any cylindrical symmetry. In this way, it is possible to adapt the tank shape to the motor vehicle geometry by a suitable selection of the individual containers.
Especially in the case of an amply-sized, flat type of design of this storage container, however, precautions must be taken to accommodate the high compressive forces that act on the walls of the outside container. Thus, according to DE-OS 195 24 681, supports are provided for bracing the outside container against the inside container. For these supports, a material having a low thermal conductivity is specifically selected; nevertheless a considerable amount of heat continues to be transferred into the stored cryogenic liquid via these supports.
An object of this invention is, therefore, to provide a storage container of the type mentioned above, whose geometry can be matched to a large extent to the respective space conditions and requirements, and whereby the introduction of heat into the inside container is reduced.
Upon further study of the specification and appended claims, other objects and advantages of the invention will become apparent.
These objects are attained according to the invention by providing that the support for bracing the outside container are not heat-conducting connections between the inside container(s) and the outside container.
According to the invention, the shape of the outside container (or shell) can be selected at will and thus optimally matched to the space that is provided for the storage container. To take up the liquid that is to be stored, one or more inside containers are provided, whose geometry is essentially independent of that of the outside container. The atmospheric forces that act on the outside container are taken up by bracing supports that are arranged according to the invention such that they do not make any contribution to the heat conduction between the inside and the outside container.
Of course, even in the design according to the invention, positioning supports are necessary to keep the inside container positioned within the outside container. These positioning supports are not, however, designed for bracing against the compressive forces. Consequently, the positioning supports can be relatively thin compared to the bracing supports whereby heat transfer via these positioning supports is negligible.
The positioning supports are in contact either only with the outside container or only the inside container(s). If only one inside container is provided, the positioning supports preferably connect opposing walls of the inside container to offset the tensile forces that are induced by the vacuum that surrounds the inside container. Analogously, the bracing supports that stabilize the outside container preferably run between opposing walls of this container. In the case of several inside containers, the positioning supports can be attached either inside a container or can surround the latter in the form of a stabilizing skeleton or else can advantageously position the inside container vis-a-vis another inside container.
To be able to store a large amount of cryogenic liquid, it is advantageous to match the shape of the inside container to that of the outside container in order to make optimal use of the space available. In this case, however, attention must be directed to the fact that an insulation space remains between the two containers. Generally, supports for the inside and the outside containers must be provided in this case. In this design, the inside container has through-ducts or recesses for the bracing supports of the outside container, so that the bracing supports of the outside container do not come into heat-conducting contact with the inside container.
From a design standpoint, it has proven advantageous to provide not only one but rather several inside containers in a common outside container. In this case, shape and size of the individual inside containers are advantageously matched to the shape of the outside container so as to attain optional use of the volume of the outside container. The use of several inside containers has several advantages. Standard containers, such as, e.g., cylinders, can be used; the geometry of the inside containers can be selected so that the latter tolerate the pressure differences that are present in the storage container without additional supports, and the space that remains free between the individual inside containers is available for guiding the supports for the outside container.
In the case of several inside containers, the latter are preferably connected together on the liquid and/or gas side. In this way, for example, only a single filling level display or only one pressure gauge is necessary for all inside containers.
The inside container or containers has or have preferably a round or elliptical cross-section, since the latter are especially pressure-stable.
The invention has proven its value especially in the storage of liquid hydrogen, liquid oxygen, liquid nitrogen, liquid helium and LNG. The storage container according to the invention is not advantageous, however, only for storing cold media, but also for storing warm or hot media. The invention can always be used advantageously if there is a clear temperature difference between the medium, liquid or gas, that is to be stored. The high adaptability of the storage container to the most varied spaces offered is especially advantageous when using these storage containers in motor vehicles, especially land vehicles.